Function monitoring systems for display at a convenient location are widely used in a variety of applications. Typically, the modern passenger automobile includes a number of different instruments used to monitor various functions of the automobile. For example, a speedometer and odometer combination is used to record instantaneous speed and the total number of miles traveled, respectively. In addition, instruments or warning lights are generally provided for displaying monitored conditions of oil pressure, remaining fuel capacity, alternator charging, coolant temperature, brake system functions, and the like.
Generally, all of the instruments or warning lights for these various functions are clustered together at a convenient point for ready and frequent review by the driver of the vehicle. Similar systems also are provided for aircraft, trucks and boats. In addition, modern cooking stoves and ovens provide various indicia of whether or not a particular unit is operating at any given time and further provide indicia by means of suitable display panel instrumentation of elapsed time counters, oven temperature displays and the like.
With the rapid increase in the use of recreational vehicles and boats capable of operating as independent mobile dwellings, additional need has arisen for monitoring various functions of the equipment used in such recreational vehicles and boats. Typically, these vehicles are self-contained small homes with water, sewage facilities, heating and cooling systems, propane gas cooking systems and other systems, depending upon the degree of sophistication of the particular motor home or recreational vehicle which is involved.
In the past, the monitoring instruments for the different functions or systems in mobile homes and recreational vehicles have not been conveniently placed at a single location for frequent observation and monitoring. In addition, the different functional systems have utilized different types of display and in many cases, no display at all for some functions. For example, the propane gas supply often is merely indicated by a simple analog gauge located near or on the propane tank itself. Although the generator units for recreational vehicles and motor homes require regular servicing after a relatively low number of hours of operation, no measurement of the actual hours of use is usually employed. Instead, it is necessary for the user of the vehicle to try to remember how many hours the generator has been run in order to determine when it is necessary to service the generator. This is highly inefficient and very often leads to cases where no required regular maintenance is effected; and the only time the generator is serviced is when there is a failure, often caused by lack of regular maintenance.
A particularly irritating problem in the use of recreational vehicles and mobile homes arises in keeping track of the reserve water supply and the state of the holding tanks used to temporarily store the sewage. In most cases, guesswork, based on past experience of use, is the only way of ascertaining how much fluid remains in the water supply tank or is present in the holding tanks. Generally, when this technique is employed, a person does not realize he is out of water until the water tank runs dry or that the holding tanks are full until they actually overflow or are nearly ready to do so. Neither of these conditions is tolerable for enjoyable use of the motor home.
Systems for providing indications of the liquid levels in the holding tanks and in the water tanks of mobile homes have been devised in the past. Generally, these systems employ different sets of spaced electrical contacts in the water tank and holding tanks. The contact sets are located at levels in the tanks indicative, for example, of one-fourth, one-half, and three-fourths levels of fullness. Direct current circuits connected across the contact sets in series with indicating lights or other direct current display instrumentation is employed. When the liquid level bridges the different sets of contacts, the indicator lights are illuminated; so that the user can have a fair idea of the remaining water supply in the water tank or the reserve capacity remaining in the holding tanks. A problem arises with the use of such indicating systems, however, inasmuch as the direct current flowing through the contacts causes electrolysis of the contacts, resulting in their relatively rapid deterioration. For mobile homes which are extensively used, the indicating systems often deteriorate to an unusable or unreliable condition within less than a year. When the electrolysis of the contacts reaches a point where they become unreliable, it is necessary to completely overhaul that portion of the system at substantial expense.
As a consequence, it is desirable to cluster the display indicia for monitoring various functions in a mobile home or recreational vehicle at a single convenient location and to improve the operation and reliability of the monitoring system itself in a manner which overcomes the disadvantages of the prior art systems mentioned above.